This invention relates to hydraulic nuts and, more particularly, this invention relates to a device and method for mounting and dismounting a bearing on a tapered shaft or the like.
Hydraulic nuts per se are well-known in the art. They are used, for example, to assist in mounting and dismounting bearing assemblies on shafts, especially tapered shafts. A bearing assembly can be mounted on a shaft, in particular a tapered shaft, only to a point where the press fit becomes too tight to axially slide the bearing assembly any further. Yet, the position may not be correct or, in the case of a preloaded bearing, the preload might not be correct and, therefore, the clearance may not be correct. Hydraulic nuts are often used to easily and precisely position a bearing assembly on a shaft. U.S. Pat. No. 5,685,068, for instance, teaches the use of a hydraulic nut to assist in mounting bearings on a tapered shaft. U.S. Pat. Nos. 4,611,351 and 5,743,016 teach the use of a hydraulic nut for mounting preloaded bearings on a shaft. U.S. Pat. No. 3,033,597 teaches the use of a hydraulic nut to mount and dismount gears on a shaft.
A typical arrangement using a hydraulic nut to assist in mounting a bearing assembly on a tapered shaft is shown in FIG. 1. There is shown a bearing assembly generally designated by the numeral 50 press fit onto a shaft 52. Spherical roller bearings are shown but other types of bearings such as double row ball bearings are often mounted in the same manner. Bearing assembly 50 comprises an inner ring 54 having a pair of inner raceways 56 and an outer ring 58 having a pair of outer raceways 60. Rolling elements 62 are disposed between opposed inner and outer raceways 56 and 60. Bearings 62 could be spherical roller bearings or ball bearings. As can be seen in FIG. 1, the inner ring 54 of bearing assembly 50 can be mounted on the shaft 52 to a press fit only to a certain point without applying additional pressure to move it to the desired position or to apply the required amount of preload and to take out the clearance.
To that end, a hydraulic nut generally designated by the numeral 64 is used. Hydraulic nut 64 comprises a nut body 66 which has internal threads and is screwed onto a portion 68 of shaft 52 which is externally threaded. Nut body 66 has an annular chamber 70 which is coaxial with the nut body and is operatively connected to a source of fluid pressure (not shown) through a suitable connector and fluid passage 72. While passage 72 is shown as an axially directed passage, it can equally well enter the nut body from a radial direction. The fluid is typically an oil but can be any fluid well-known in the art for the purpose. An annular piston 74 which could have an inwardly directed flange 76 is seated in chamber 70. Piston 74 abuts inner ring 54. Alternatively, the piston 74 could rest against an adapter sleeve which, in turn, rests against the inner ring, as shown in U.S. Pat. No. 3,957,319. Fluid pressure is applied to the hydraulic nut 64 to force piston 74 to the left as seen in FIG. 1, thereby applying sufficient uniform pressure to inner ring 54 to push the bearing assembly further onto shaft 52. When the bearing assembly 50 has reached the desired position or has achieved the desired preload and clearance, the fluid pressure is relieved. The hydraulic nut could be removed or could be left in position if it could serve some other purpose.
The aforementioned prior art is concerned with providing methods and means for mounting bearings, gears, or the like, on shafts; they are not drawn to the measurement of the amount of pressure to be applied while doing so. U.S. Pat. No. 5,779,419 (hereinafter referred to as “the '419 patent”) teaches a hydraulic nut which includes means for indirectly measuring the axial displacement of the piston with respect to the nut body. In this construction, the piston has an outwardly extending annular flange and the nut body has a through-bore which is partly threaded and aligns with the outwardly extending flange. A distance measuring device comprising a dial indicator, a screw threaded housing, and a sensing pin is mounted in the bore with the sensing pin bearing against the outwardly directed flange. As the piston moves under the oil-pressure generated force, the sensing pin moves with it and a reading is made from the dial indicator. Indicator readings are converted to useful dimensional units by reference to a table of values which have been determined empirically.
While the device of the '419 patent is an improvement over the devices theretofor in use, it must be kept in mind that major users of the device are maintenance personnel and its use is unduly complicated and time consuming for those users. After taking a reading from the dial it is necessary to refer to calibration tables provided by the manufacturer to calculate the distance travelled or other useful information. That means that the pressure must be occasionally paused and a measurement taken and then reference must be had to the calibration tables and the internal clearance must be measured with feeler gauges. The process is repeated until the desired axial movement is achieved and, more important, the clearance is taken out. The U.S. patents mentioned herein are all incorporated by reference in their entireties.
Accordingly, it is an object of the present invention to provide a device and method for measuring the axial movement of a bearing, gear, or the like on a shaft, in particular a tapered shaft, which is free of the aforementioned and other such disadvantages.
It is another object of the present invention to provide a device and method for directly measuring the axial movement of a bearing, gear, or the like on a tapered shaft.
It is still another object of the present invention to provide a device and method for directly measuring the axial movement of a bearing, gear, or the like on a tapered shaft which is simple and convenient to use.
Consistent with these and other objects, the present invention provides a hydraulic nut comprising:
(A) an annular nut body having a thickness T and having an annular chamber in one face thereof;
(B) a piston coaxially disposed in said chamber and axially displaceable therein, said piston having a radially extending protrusion;
(C) a displacement bar removably mounted on said protrusion and extending across the periphery of said nut body in a direction substantially parallel to the axis of said nut body;
(D) said displacement bar having a length L=T+a where a is a predetermined distance for axial movement of said piston.
It is most preferred that the nut body of the hydraulic nut is internally threaded.
As with the prior art hydraulic nuts, the nut body further comprises a fluid passage operatively communicating with the chamber and has a fitting for connection to a fluid source under pressure communicating with the passage.
The protrusion on the piston preferably comprises a pair of opposed lugs defining a slot therebetween. The lugs each have a through bore, the displacement bar has a through bore at one end thereof, the displacement bar is disposed in the slot with the through bores in alignment, and a locking pin is inserted in the bores to secure the displacement bar in place. Those skilled in the art will appreciate that any suitable configuration for mounting the displacement bar could be used. For example, the protrusion could be a single lug with a threaded hole and the displacement bar could have a threaded end or stud to screw into the threaded hole.
In its preferred configuration, the piston could further comprise an inwardly directed annular flange to make better contact with the inner ring of the bearing.
In another configuration, the piston can further comprise an outwardly directed annular flange, wherein the protrusion extends outwardly from the flange.
In cases where an adapter sleeve is used, the hydraulic nut is threaded onto the adapter sleeve which, in turn, is fit onto the shaft which typically is unthreaded.
For removal of a bearing assembly from a shaft, a removal sleeve is inserted between the shaft and the bearing assembly by use of the hydraulic nut and with the bearing held stationary. A hydraulic nut is then screwed onto a threaded end of the removal sleeve to force the removal sleeve off the shaft. To assemble the bearing on the removal sleeve, a hydraulic nut is threaded on the threads of a shaft. The hydraulic nut piston is then pushed against the removal sleeve while the bearing is held stationary.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings where like numbers indicate like parts.